12S29 Santa María
Santa María Also known as: - *Gagxanul, "The Naked Volcano" - Santiaguito (The dome extruded since 1922) Location/Geological Setting: Santa María/Santiaguito's position along the northern extent of the Central American volcanic arc. It is a large active volcano in the Western Highlands of Guatemala, close to the city of Quetzaltenango. Facts: 1) Altitude - Height of the top above sea level: 3772 m 2) Formation - The volcanoes are formed by the subduction of the Cocos Plate under the Caribbean Plate. 3) Volcanic Vent - In 1922, a new volcanic vent formed in the enormous crater, and formed a new volcano, named Santiaguito. - The cone is a few hundred metres tall, reaching an elevation of about 2,500 metres. Pre- Eruption: - Following the cone-building eruptions, activity seems to have changed to a pattern of long periods of repose followed by the emission of small lava flows from vents on the flanks. - The cone built by the eruptions had a volume of about 10 cubic kilometres, and consisted of a mixture of basalt and andesite lavas. - Before 1902 the volcano had been dormant for at least 500 years and possibly several thousand years - Early signs such as seismic swarm in the region started in January 1902. Eruption: - The first eruption of Santa Maria in the recorded history occurred on 24 October 1902. - One of the three largest eruptions of the 20th century - Third large eruption of that one year, after Mount Pelée in Martinique and Soufrière in St. Vincent. - One of the five biggest eruptions of the past 200 (and probably 300) years. The eruption blasted away most of one side of the 3,772-metre tall mountain. - Some 5.5 cubic kilometres of volcanic material was ejected during the 19-day eruption - Ash column reached heights of up to 28 kilometres. Effects of the Eruption: - Steam rises from Santiaguito. - The area of the flank destroyed by the 1902 eruption can be clearly seen. - Lahar deposits snake down river valleys to the left of the Santa María is of the Sierra Madre range of volcanoes, which extends along the western edge of Guatemala, separated from the Pacific Ocean by a broad plain. - The pumice formed in the climactic eruption fell over an area of about 273,000 square kilometres - Volcanic ash detected as far away as San Francisco, 4,000 kilometres away. - The eruption tore away much of the south-western flank of the volcano, leaving a crater about 1 kilometre in diameter and about 300 metres deep. - Due to the lack of volcanic activity at Santa María, local people did not recognise the preceding seismicity as warning signs of an eruption. - At least 5,000 people died as a result of the eruption itself - Subsequent outbreak of malaria killed many more. Mitigation efforts 1. A volcanic risk map has been designed - Different from volcanic hazard maps - Takes into account the standard of living, population density, infrastructure and land use - Enables us to calculate the real cost of living near the Santa Maria Volcano - Offers special advantages in Volcanic Hazard Communications efforts - Used to forecast the cost of volcanic activity, which may be helpful in securing budgeting for mitigation efforts - Used for planning mitigation expenditures as sensitivity analysis of uncertainties in hazard zonation or recurrence intervals of various types of activity can be tested against economic and population data for cost effectiveness. 2. Remote sensing The value of remote sensing as a hazard mitigation tool at volcanoes is not directed at measuring things that forecast volcanic activity, but at mapping the changes resulting from activity that are and may be associated with subsequent hazard.